Carbon Footprint Assessment Method And Case Study Of Intensive Pig Production System In China

The number of pigs raised in China accounts for 50%of the global pig production.However,few studies on carbon footprint?CF?of large-scale pig production based on China's actual production conditions were carried out.Hence,a CF assessment method for large-scale pig production systems was established in this study based on life cycle assessment?LCA?methods and the production of typical pig farms.To find mitigation measures,a typical large-scale pig farm in Northern China were used for selection of different allocation methods for feed crops and assessment of greenhouse gas?GHG?emissions or CF of pig production system.The main conclusions are as follows:?1?The system boundary of the pig supply chain ranged from feed production to farm gate in this study,including feed production module and animal production module.GHG emissions from the agricultural materials production,energy consumption of agricultural machineries,processing and transport in feed production module were calculated by using production activity data multiplied the corresponding emission factors.The calculation of N₂O emissions from nitrogen fertilizers application was based on IPCC?2006?.Emissions from enteric fermentation and manure management in animal production module were calculated using Tier 2 of IPCC?2006?for different species/category of pigs.One year was taken as the time boundary and 1 kg live weight?LW?was chosen as the functional unit in the this LCA study.Three types of GHG?i.e.CO₂,CH₄,N₂O?were assessed.When available,published data reflecting domestic production practices were used as the parameters for GHG emission calculations.When not available,data according to expert recommendations or through indirect calculation were used.?2?This study examined the impacts of six typical GHG allocation methods?mass,energy,protein,hybrid of energy+protein,economic value,and no allocation?for production of major feedstuff used in an intensive swine operation in Northern China.The no allocation method could not reflect the multipurpose characteristics of feed crop planting.Economic allocation may be chosen for evaluation of activities related to the economic value of GHG.Physical allocation including mass,energy,protein,hybrid of energy+protein is more suitable for reflecting the changes of outputs from feed crop planting.Mass allocation,as the basis for all allocation methods,is recommended for evaluation of CF when the feed crop properties are unknown.The results showed that the different allocation methods led to a CF ranging from 2.72 to 4.64 kg CO₂-eq per kg of live weight?LW?of market pig?110 kg?,with the minimum CF?2.72?corresponding to the mass allocation and the maximum CF?4.64?to no allocation.Regardless of the allocation methods used,feedstuff production was the largest CF source of the pig production chain,accounting for 46⁶6%.The second largest CF source was manure management?21³4%of total CF?.?3?On basis of collecting the annual production data of typical pig farm and the large amount data of agricultural inputs from national typical feed crops,the CF assessment method established in this study above was adopted,the CF associated with the whole process of pig production of a typical large-scale pig farm in Northern China was assessed,including feed production?crop planting,feed processing,and transportation?,enteric fermentation,manure management and energy consumption.The results showed a CF of 2.72 kg CO₂-eq per kg of live market pig,and relative contributions of 46%,34%,15%,and 5%to the total CF by feed production,manure management,farm energy consumption,and enteric fermentation,respectively.Long-distance transport of semi-raw feed materials caused by planting-feeding separation and over-fertilization in feed crop planting were two main reasons for the largest contribution of GHG emissions from feed production for the total CF.Crop planting accounted for 73%of the feed production CF,while feed processing and transportation accounted for the remaining 27%.If the amount of nitrogen fertilizer used for producing the main feed ingredients is reduced from 209 kg/ha?for corn?and 216 kg/ha?for wheat?to 140 kg/ha?corn?and 180 kg/ha?wheat?,respectively,the total CF would be reduced by 7%.If transportation distance for feed materials decreased from 325-493 km to 30 km,along with reducing the number of empty vehicles for the transport,total CF would be reduced by 11%.In addition,use of pit storage–anaerobic digestion–lagoon practice can reduce GHG emissions from manure management by 76%as compared to the traditional pit storage–lagoon manure treatment method.